DL-Phenyl-d5-alanine is widely used in research and development, particularly in the fields of biochemistry and pharmacology. It serves as a stable isotope-labeled compound, making it valuable in metabolic studies and drug testing. Researchers utilize it to trace and analyze metabolic pathways, providing insights into how phenylalanine is processed in the body. Additionally, it is employed in the synthesis of labeled peptides and proteins for use in NMR spectroscopy and mass spectrometry, aiding in structural and functional studies. Its deuterium labeling also makes it useful in pharmacokinetic studies to understand the absorption, distribution, metabolism, and excretion of drugs.